Estimated water requirements for gold heapleach operations. Run time,ph,and temperature are the keys to using thiosulfate. Anodic polarization, cathodic polarization and leaching experiments were included in this study. The ammonia thiosulfate system with copper offers high gold leaching rates compared to the cyanide system, because the reaction is catalyzed by cupric ions. The gold industry has been seeking alternative reagents for leaching gold from lowgrade ores for the past 25 years. Mineralogical studies on the concentrate showed that very fine gold grains 10. Leaching of pcbs with sodium thiosulfate and ammonium thiosulfate in this step, sodium and ammonium thiosulfate were used to extract gold and silver of whole pcbs. A process of biooxidation followed by thiosulfate leaching of gold from refractory gold concentrate was investigated.
Goldstrike ore was leached using either an ammoniacal thiosulfate system or a sodium cyanide system. It has the advantages of fast gold leaching speed and nontoxicity. This worldwide phenomenon is the driving force for the development of alternative technologies for the leaching and recovery of gold from socalled double refractory ores. At best, leaching achieved 2,98 mghcm2 with ammonium thiosulfate and 2,68 mghcm2 with sodium thiosulfate. Thiosulphate leaching is a process that removes gold from gold bearing ores without the use of cyanide. I know there is a way because it is used in gold leaching as an alternative to cyanide in mining operations.
Despite the fact that the gold mining industry accounts for only % of total cyanide consumption there is growing public concern over the use of toxic cyanide for gold extraction. The oxidant can directly consume thiosulfate or facilitate side reactions other than gold oxidation. Crush your ore to the consistency of fine sand in a rod mill, then transfer it into a large vat with a strong solution of sodium thiosulfate and agitate it with paddles for a day to a week, depending on the size of your vat. Thiosulfate leaching offers a number of benefits related to gold recovery yields and environmental concerns. Barrick gold recently commercialized a unique calcium thiosulfate leaching plant to treat. If you let your leach run too long,and let the ph drop too much during run time,it will then pull in some iron. Thiosulfate leaching can be considered a nontoxic process, the gold dissolution rates can be faster than conventional cyanidation and, due to the decreased interference of foreign cations, high. Us6632264b2 gold recovery from thiosulfate leaching. Its advantage is that it can form stable complexes with gold. Thiourea as an additive to thiosulfate solutions was seen to disrupt ss bonding in both aus8 and au2ssn surface structures. Thiosulfate leaching can be considered a nontoxic process, the gold dissolution rates can be faster than conventional cyanidation and, due to the decreased interference of foreign cations, high gold recoveries can be obtained from the thiosulfate leaching of complex and carbonaceoustype ores. The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore.
The iodineiodide gold leaching is well known as an effective and environmentalfriendly method for gold leaching without toxic chemicals such as cyanide, aqua regia and mercury 3, 5. Ammonium thiosulfate ecological alternative to replace sodium. Thiosulfate leaching of gold ores has great potential to reduce the impact on the environment. The resultant solution, after proper dilutions were made, was analyzed for cu, co, ni, mn and fe with an inductively coupled plasma. The hydrometallurgical leaching of native gold from gold bearing ores or the dissolution of gold metal during the recycling of electronic and precious metal scrap is performed every day using hazardous chemicals such as sodium cyanide or aqua regia.
Thiosulphate stability in gold leaching process bibliotheque et. An update useful for further research in noncyanide gold lixiviants. Gold and silver leaching in thiosulfate solution is preferable kinetically and environmentally if conducted in a closed vessel system. The only smell present during the leach time is ammonia. The current problem of thiosulphate gold leaching is the high reagent consumption, to understand the decomposition chemistry of thiosulphate, solution stability tests were conducted in open and sealed vessek mder ambient temperature. Gold sodium thiosulfate is a fairly common sensitizer with elicitation of symptoms linked to gold in jewelry, occupational exposure to gold, dental restorations, gold plated. Effect of additives on thiosulfate leaching of a gold ore. However, such work is of limited value, since the proper study. Gold cyanidation also known as the cyanide process or the macarthurforrest process is a hydrometallurgical technique for extracting gold from lowgrade ore by converting the gold to a watersoluble coordination complex. Spectroelectrochemical studies of surface species in the.
Not surprisingly then, other researchers have studied the oxidation of gold in thiosulfate solutions jiang et al. Gold leaching requires a ligand and an oxidant as indicated in eq. The cost and transport of cyanide, the poor recovery of gold from carbonaceous ores, the lack of selectivity of cyanide towards copper minerals and the cost of waste treatment are real factors which can make cyanide unattractive in some circumstances. May 27, 2017 crush your ore to the consistency of fine sand in a rod mill, then transfer it into a large vat with a strong solution of sodium thiosulfate and agitate it with paddles for a day to a week, depending on the size of your vat. The kinetics and mechanism of gold leaching in the ammonia thiosulfate copper atscu system have been studied using the rotating electrochemical quartz crystal microbalance reqcm. Biooxidationthiosulfate leaching of refractory gold concentrate. Gold recovery from refractory gold concentrates by.
The complexity of thiosulfate leaching of gold is exemplified in figure 1 14. Gold sodium thiosulfate is a fairly common sensitizer with elicitation of symptoms linked to gold in jewelry, occupational exposure to gold, dental restorations, gold plated intracoronary stents and previous rheumatoid arthritis treatment. Read product labels carefully and talk to your doctor if you have any questions. The effect of concentration of different reagents, applied potential, ph, temperature, and electrode rotating. Since the 1880s, cyanidation has been the main method for the extraction of gold and silver from a wide range of ores, because of its high extraction efficiency and costbenefit ratio. Jul 16, 2016 leaching by thiosulfate decreases interference from these foreign cations. High consumption of reagents and the lack of a cheap process for recovering gold have made thiosulfate leaching. Has anyone found a real working precipitation process to recover the gold,that works well,and is dependable. It shows that sulfite, sulfide, sulfate glycine and ethylenediaminetetracetic acid edta have beneficial effects on gold extraction, compared to standard thiosulfate leaching with 0. The current problem of thiosulphate gold leaching is the high reagent.
Sodium thiosulfate is used in gold mining, water treatment, analytic chemistry, the development of silver based photographic film and prints, and medicine. Thiosulphate is a more effective lixiviant of pregrobbing and highcopper ores than cyanide because ammoniacal thiosulphate leaching is less sensitive than cyanidation to. It is currently the main gold leaching process in the world. The role of ligands and oxidants in thiosulfate leaching of gold.
Effect of additives on thiosulfate leaching of a gold ore s. The processes include subjecting the gold bearing and copperbearing thiosulfate solution to a ph andor temperature adjustment to reduce tetrathionate concentration in the thiosulfate solution prior to contacting with an ion. The effect silver alloyed with gold was evaluated and the result showed that the dissolution rate of pure gold is higher than that form 4 and 8 wt% ag alloys. Bioleaching, chlorination, aqua regia, bromine, thiocyanate, thiosulfate and thiourea leaching. The exact reason for this is unclear and further investigation is necessary. Kinetics of the carbonate leaching for calcium metavanadate. Figure 46 effect of sodium sulphite concentrations on thiosulphate.
Recovery of gold from thiosulfate solutions and pulps with anion. Investigation into the use of electrochemical extraction. The results for leaching gold with alternative reagents, sodium thiosulfate and ammonium hydroxide, show that the best extraction was achieved at 0. The significant consumption of thiosulfate during leaching of gold may be caused by complexation with different metal ions. Processes for recovering gold from copper gold ores thiosulfate leaching or gold ores copper catalyzed thiosulfate leaching using ion exchange technology are disclosed.
At full capacity,400 tons of ore can be processed daily, with leaching taking place simultaneously in two sets of seven tanks. Although not as aggressive a leaching agent as cyanide, thiosulphate offers several technological advantages including its lower toxicity and greater efficiency with gold deposits associated with pregrobbing ores. Within the tanks, the slurry interacts with thiosulfate and a fine, beadlike material called resin that collects the gold. Many researchers have identified that thiosulfate leaching is the most likely alternative to cyanidation due to nontoxicity, low cost and other benefits. In the sodium thiosulfate and ammonium thiosulfate tests, it was possible to extract 70 and 75% of the gold contained in the pcb, respectively, using solutions containing 0. The medical uses of sodium thiosulfate include treatment of cyanide poisoning and pityriasis. After leaching, leach liquor was filtered using whatman 42 filter papers and the collected residue was digested in 1. The reduction of gold thiosulfate was studied as an alternate gold complex for plating baths. Au s o present in the solutions produced by leaching gold ores in an ammonia thiosulfate media, where copper is the main impurity in the system. Case report an 80yearold gentleman presented to our clinic with a twoyear history of pain to the midanterior mandible.
There was a distinct disappearance of gold after each batch reactor experiment. Most published studies on gold leaching with thiosulfate focus on gold ores. Thiosulphate leaching of precious metals has been developed as an. The gold leaching rate in ammonium thiosulfate in the presence of copper species is mainly controlled by the cathodic process, which is under diffusion or mixed kinetics control. Fundamental aspects of gold leaching in thiosulfate solutions. An improved thiosulphate leach process for the recovery of gold from ores and other gold bearing materials, characterised in that the leach solution comprises thiosulphate, thiourea or a reagent chemically related thereto, and an oxidant that does not oxidise thiosulphate, the process producing a pregnant leach solution from which gold may be recovered.
The proposed method of the gold recovery comprises leaching with a solution of a mixture of sodium and ammonium hydrosulfite and thiosulfate, by sorption of the thiosulfate gold complex on a highly basic anion exchanger and by isolation of the highly basic anion exchanger, the sorption being carried out 210 hours after the leaching. In addition, thiosulfate can be cheaper than cyanide. If signs of cyanide poisoning reappear, repeat treatment using onehalf the original dose of both sodium nitrite and sodium thiosulfate. Leaching of the carbonaceous matter was conducted in batch experiments, as well as in columns at various flow rates to compare the mass of gold leached from the carbonaceous matter to its initial gold content. However, gold cyanidation process has serious environmental risks if an accident occurs in the process because of the toxicity of cyanide. Since the leaching of gold in thiosulfate solutions is a corrosion reaction, it can be studied using stand ard electrochemical techniques. However, in alkaline solutions, oxidization of copper by thiosulfate is much slower zhang, 2004.
All of my observations are with sodium thiosulfate. Ammonium thiosulphate is an alternative gold leaching laaviant used to replace cyanide. Sgs is a global technical leader in the field of thiosulphate leaching, and our. Ammoniacal thiosulfate and sodium cyanide leaching of preg. Thiosulfatecopperammonia leaching of pure gold and. If you have an allergy to sodium thiosulfate or any other part of sodium thiosulfate. It is the most commonly used leaching process for gold extraction production of reagents for mineral processing to recover gold, copper, zinc and silver represents. Sodium thiosulphate gold leaching 911 metallurgist. Gold leaching, thiosulfate, additives, leaching kinetics, thiosulfate stability.
Electrochemical study of gold leaching in thiosulfate. Wo2005017215a1 improved thiosulphate leach process. Gold recovery using the heap leach method is based on the process of applying a leachate that usually contains about 100 to 600 parts per million ppm 0. Thiosulphate stability in gold leaching process 911 metallurgist. Adsorption of copper from an ammoniathiosulfate media. Whether the leaching is performed in stirred tank reactors or heaps, the size and type of equipment needed for a thiosulphate leaching flowsheet is very similar to a conventional cyanide leach.
In the present paper the possibility of extracting gold by electrochemical leaching using a solution of sodium thiosulfate has been studied. After roasting and oxidizing, the gold leaching rate increases substantially. The results of the rotating gold disk leaching study are consistent with those from the electrochemical study. A method for leaching or dissolving gold from ores or. Electrochemical study of the gold thiosulfate reduction. The processes include subjecting the gold bearing and copperbearing thiosulfate solution to a ph andor temperature adjustment to reduce tetrathionate concentration in the. Thiosulphate leaching for gold hydrometallurgy sciencedirect. For this propose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view. It is on the world health organizations list of essential medicines. In a resinin leach system, full gold recovery was also achievable with sufficient resin after 24 h leach with 0. Associated sulfide minerals in thiosulfate leaching of gold. Feng university of science and technology, liaoning, anshan, china received august 15, 2017, revised november 15, 2017 the effect of additives on gold leaching was investigated using ammonium thiosulfate or calcium thiosulfate. Jan 22, 2020 sodium thiosulfate 1 mlkg of body weight 250 mgkg or approximately 3040 mlm 2 of bsa not to exceed 50 ml total dose immediately following administration of sodium nitrite.
The role of ligands and oxidants in thiosulfate leaching. In both leachates, the effect of adding copper, as a catalyst agent, and hydrogen peroxide, as the oxidizing agent to the reaction were evaluated. The conventional cyanidation process in gold leaching has been used since 1887. The processing of gold is becoming more complicated due to the increasingly complex nature of the remaining gold bearing ore bodies. Nov 21, 2014 ammonium thiosulfate ecological alternative to replace sodium cyanide in gold and silver dissolution in lowgrade ores, m. Thiosulfatecopperammonia leaching of pure gold and pressure.
I have a few pieces of computer parts that i would like to extract the gold from. Ru2125107c1 hydrometallurgical recovery of precious metals. Also getting the gold out of the precipitates seems to be a real pain. In the case of the gold leaching process using thiosulfate, copper oxidation by thiosulfate deserves special attention because it is a thermodynamically favored reaction. Tosawadissolution of gold in ammoniacal sodium thiosulphate solution. The reduction voltammograms were obtained on a stationary gold electrode at ph 4. The modes of gold loss in the calcium thiosulfate leaching. Leaching of gold and silver from printed circuit board of. I heard that you can leach it out with sodium thiosulfate which makes a strong complex of gold ions to make aus2o323 is there a way you can get it out of this form. Gold recovery from ammoniathiosulfate leaching solution. Study on gold extraction from thiosulfateethylenediamine. G babayanthe kinetics of the dissolution of gold and silver in sodium thiosulfate solutions.
Has anyone here actually used thiosulfate for leaching gold ore,and had positive results,that can be repeatable as a real leaching process. In batch reactor experiments the best yield was 88 %. Pdf gold dissolution in nonammoniacal thiosulphate solutions. The role of oxygen in thiosulphate leaching of gold request pdf. Gold leaching in thiosulfate solutions and its environmental. These chemicals represent health and safety risks for workers and a serious threat for the.364 661 313 1454 721 635 784 1039 1333 1217 486 743 579 705 1186 147 1196 367 860 1197 234 703 552 1481 90 1064 862 710 609 756 784 787 1458 672 1457 1487 837 224 691 1445